no recursive interrupts

0b75a8e8 · rsc · 5a71f933 · 0b75a8e8
--- a/trap.c
+++ b/trap.c
@@ -18,10 +18,9 @@ tvinit(void)
 {
  int i;

-  for(i = 0; i < 256; i++){
-    SETGATE(idt[i], 1, SEG_KCODE << 3, vectors[i], 0);
-  }
-  SETGATE(idt[T_SYSCALL], 1, SEG_KCODE << 3, vectors[T_SYSCALL], 3);
+  for(i = 0; i < 256; i++)
+    SETGATE(idt[i], 0, SEG_KCODE << 3, vectors[i], 0);
+  SETGATE(idt[T_SYSCALL], 0, SEG_KCODE << 3, vectors[T_SYSCALL], 3);
 }

 void
@@ -34,9 +33,9 @@ void
 trap(struct trapframe *tf)
 {
  int v = tf->trapno;
+  struct proc *cp = curproc[cpu()];

  if(v == T_SYSCALL){
-    struct proc *cp = curproc[cpu()];
    if(cp->killed)
      proc_exit();
    cp->tf = tf;
@@ -46,9 +45,15 @@ trap(struct trapframe *tf)
    return;
  }

-  if(v == (IRQ_OFFSET + IRQ_TIMER)){
-    struct proc *cp = curproc[cpu()];
+  // Increment nlock to make sure interrupts stay off
+  // during interrupt handler.  Must decrement before
+  // returning.
+  cpus[cpu()].nlock++;
+
+  switch(v){
+  case IRQ_OFFSET + IRQ_TIMER:
    lapic_timerintr();
+    cpus[cpu()].nlock--;
    if(cp){
      // Force process exit if it has been killed
      // and the interrupt came from user space.
@@ -63,27 +68,22 @@ trap(struct trapframe *tf)
        yield();
    }
    return;
-  }

-  if(v == IRQ_OFFSET + IRQ_IDE){
+  case IRQ_OFFSET + IRQ_IDE:
    ide_intr();
-    cli(); // prevent a waiting interrupt from overflowing stack
    lapic_eoi();
-    return;
-  }
+    break;
  
-  if(v == IRQ_OFFSET + IRQ_KBD){
+  case IRQ_OFFSET + IRQ_KBD:
    kbd_intr();
-    cli(); // prevent a waiting interrupt from overflowing stack
    lapic_eoi();
-    return;
-  }
+    break;
  
-  if(v == IRQ_OFFSET + IRQ_SPURIOUS){
+  case IRQ_OFFSET + IRQ_SPURIOUS:
    cprintf("spurious interrupt from cpu %d eip %x\n", cpu(), tf->eip);
-    return;  // no eoi for this one.
-  }
+    break;
    
+  default:
    if(curproc[cpu()]) {
      // assume process caused unexpected trap,
      // for example by dividing by zero or dereferencing a bad pointer
@@ -95,4 +95,7 @@ trap(struct trapframe *tf)
    // otherwise it's our mistake
    cprintf("unexpected trap %d from cpu %d eip %x\n", v, cpu(), tf->eip);
    panic("trap");
+  }
+  
+  cpus[cpu()].nlock--;
 }